We argue that, as a consequence of the graviton's spin-2, its bremsstrahlung
in trans-planckian-energy (E≫MP​) gravitational scattering at small
deflection angle can be nicely expressed in terms of helicity-transformation
phases and their transfer within the scattering process. The resulting spectrum
exhibits deeply sub-planckian characteristic energies of order MP2​/E≪MP​ (reminiscent of Hawking radiation), a suppressed fragmentation region, and
a reduced rapidity plateau, in broad agreement with recent classical estimates.Comment: 5 pages, 3 figures. Comments and references added. Typos corrected.
Fig. 3 modified. Title modified. Same as published articl